The present invention relates generally to the dissipation of heat from heat generating surfaces and objects. More specifically, the present invention relates to apparatuses for dissipating heat generated by such objects. In addition, the present invention relates to passively conducting heat away from heat generating objects by use of thermally conductive composite materials while further shielding the device from electromagnetic interference (EMI).
In industry, there are various parts and components that generate heat during operation. For example, in the electronics and communications industries, it is well known that integrated circuit components generate heat during operation. Various types of electronic device packages containing integrated circuit chips, such as satellite dishes, are such devices that generate heat. Often these devices contain integrated circuit systems with a tightly packed configuration that requires all of the components to be installed in close proximity to one another. These integrated circuit devices, particularly the main processor chips, generate a great deal of heat during operation which must be removed to prevent adverse effects on operation of the system into which the device is installed. For example, the operational section of a satellite dish, containing many integrated circuit components, is highly susceptible to overheating which could destroy the device itself or cause the components within the device to malfunction.
There are a number of prior art methods to cool heat generating components and objects to avoid device failure and overheating, as discussed above. Since the space available within these devices is generally quite limited the heat must be conducted away from the heat-generating component for dissipation at the periphery of the device. In these cases, a heat-conducting device is commonly placed into communication with the heat generating surface at one end and a heat sink at the other to dissipate the heat therefrom. Such a heat-conducting device is typically constructed from a metal casing that is charged with a conductive gas and serves primarily as a conductor with little heat-dissipating characteristic, therefore requiring the inclusion of a heat sink device in the cooling system. A heat sink typically includes a base member with a number of individual cooling members, such as fins, posts or pins, to assist in the dissipation of heat and may be incorporated into the case of the heat generating device. The geometry of the cooling members is designed to improve the amount of surface area of the heat sink that contacts the ambient air for optimal heat dissipation. The use of such fins, posts or other surface area increasing methods, in an optimal geometrical configuration greatly enhances heat dissipation compared to devices with no such additional cooling members, such as a flat heat spreader.
To further enhance airflow and resultant heat dissipation, fans and devices have been used, either internally or externally. However, these external devices consume power and have numerous moving parts. As a result, heat sink assemblies with active devices are subject to failure and are much less reliable than a device that is solely passive in nature.
It has been discovered that more efficient cooling of electronics can be obtained through the use of passive devices that require no external power source and contain no moving parts. It is very common in the electronics industry to have many electronic devices grouped on a single circuit board, such as a motherboard, modem, or xe2x80x9cprocessor cardxe2x80x9d such as the Celeron board manufactured by Intel Corporation. For example, video cards, which are capable of processing millions of polygons per second, are also susceptible to overheating and need efficient and effective cooling, as do the CPUs discussed above. Video cards typically have at least one chip thereon that runs extremely hot to necessitate a cooling system designed to operate within small clearances.
In the heat transfer industries, it has been well known to employ metallic materials for thermal conductivity applications, such as heat dissipation for cooling integrated circuit device packages. For these applications, such as device casings operating as heat sinks, the metallic material typically is tooled or machined from bulk metals into the desired configuration. However, such metallic conductive articles are typically very heavy, costly to machine and are susceptible to corrosion. Further, the use of metallic materials commonly creates electromagnetic interference (EMI), which often detracts from the performance of the device on which the heat sink is affixed. Finally, the geometries of machined metallic heat dissipating articles are very limited to the inherent limitations associated with the machining or tooling process. As a result, the requirement of use of metallic materials which are machined into the desired form, place severe limitations on heat sink and heat conductor design particular when it is known that certain geometries, simply by virtue of their design, would realize better efficiency but are not attainable due to the limitations in machining metallic articles. To compensate for these limitations, active cooling, such as by powered fans, must be employed to achieve the requisite cooling to prevent device failure.
It is widely known in the prior art that improving the overall geometry of a heat-dissipating article can greatly enhance the overall performance of the article even if the material employed is the same. Therefore, the need for improved heat sink geometries necessitated an alternative to the machining of bulk metallic materials. To meet this need, attempts have been made in the prior art to provide molded compositions that include conductive filler material therein to provide the necessary thermal conductivity. The ability to mold a conductive composite enabled the design of more complex part geometries to realize improved performance of the part.
However, a drawback in the thermally conductive molded polymer compositions, loaded with metallic reinforcing materials such as copper flakes, is that they inherently absorb EMI and radio frequency waves. As a result of their absorptive characteristics these materials effectively operate as antennas absorbing EMI that could potentially interfere with the operation of the device into which they have been incorporated. As a result, the use of these conductive polymers in devices such as satellite components and receiver equipment is undesirable.
In view of the foregoing, there is a demand for a heat dissipation assembly that is thermally conductive and capable of dissipating heat. There is a demand for a passive heat dissipation assembly with no moving parts that can provide heat dissipation without the use of active components. In addition, there is a demand for a complete heat sink assembly that can provide greatly enhanced heat dissipation over prior art passive devices with improved heat sink geometry. There is a demand for a heat sink assembly that can provide thermal conductivity and dissipation in a compact configuration. There is a further demand for a net-shape molded heat dissipation assembly that does not absorb EMI and is well suited for use in harsh environments.
The present invention employs the advantages of prior art heat transfer and dissipation devices. In addition, it provides new advantages not found in currently available devices and overcomes many disadvantages of such currently available devices.
The invention is generally directed to a novel and unique, molded thermally conductive component part that is net-shape moldable from a thermally conductive polymer composition. The part of the present invention also includes a coating of EMI reflective material. The present invention relates to a molded heat dissipating part that conducts heat from a heat-generating source, such as an integrated circuit component or electronic components on a computer circuit board, such as the operational section of a satellite dish.
The molded heat dissipation part of the present invention has many advantages over prior art in that it is injection molded from the thermally conductive polymer materials that enables the part to be made in complex geometries. These complex geometries enable the heat conductive and dissipative components of the part to be optimized to be more efficient thus transferring and dissipating more heat. As a result, the molded part is freely convecting throughout, making the part more efficient. The ability to injection mold the heat dissipation part permits the optimal configuration to be realized and achieved. Since the part is net-shape molded, valuable and costly fabrication time will be saved. Parts can be fabricated that, although complex in shape, require no additional tooling, shaping or machining steps to reach the final configuration. Parts can be designed in virtually any shape to be installed within tight clearances allowing the most efficient layout of heat generating components while still allowing heat to be conducted to the periphery of the device for effective dissipation. The present molded heat dissipation part can be designed to what is thermally efficient while allowing the device to be designed in the most efficient manner without the limitations imposed by the manufacturing and mechanical limitations of the prior art processes, such as brazing.
Another important feature of the new heat dissipating part is its ability to reflect EMI and RF waves. This is particularly important in a satellite dish environment, which is very EMI sensitive. Since the moldable conductive polymer inherently absorbs EMI and RF waves, there is a danger that this interference will be conducted back into the circuitry from which the heat is being dissipated. This interference is often problematic and prevents the device from functioning properly. To prevent the parts from absorbing EMI and RF, the part of the present invention is covered with a metallic coating to effectively reflect the EMI and RF waves and avoid the unwanted interference often encountered in telecommunications applications. A coating of nickel-copper is a preferred coating and would serve the additional function of sealing the conductive polymer against water infiltration. This would protect the device for use in potentially harsh environments similar to those in which a great deal of telecommunications equipment is currently installed.
It is therefore an object of the present invention to provide a heat-dissipating device that can provide enhanced heat dissipation for a heat generating component or object.
It is an object of the present invention to provide a heat-dissipating device that can provide heat dissipation for integrated circuit devices, such as a satellite dish or telecommunications equipment.
It is a further object of the present invention to provide a heat-dissipating device that has no moving parts.
Another object of the present invention is to provide a heat-dissipating device that is completely passive and does not consume power.
A further object of the present invention is to provide a heat dissipation device that is inexpensive to manufacture.
Another object of the present invention is to provide a heat dissipation device that has a thermal conductivity greater that conventional heat sink designs.
An object of the present invention is to provide a heat transfer part that is net-shape moldable and can be configured into complex geometries to allow optimal integrated circuit configuration.
Yet another object of the present invention is to provide a molded heat transfer part that is shielded from absorption of electromagnetic interference and radio frequency waves.